The relation of perception to memory is a fundamental characteristic of human cognition, each affecting and determining the other. This relation is explored empirically with a task known as short-term priming: Words (termed 'primes') are presented just prior to a trial, but are irrelevant to the main task. Then a target word is presented briefly and masked, and followed by two choice words, one of which had been the target. Performance is strongly affected when one or more primes are related to one or more of the choice words. Our research has been able to separate these priming effects into those due to 'preference' and those due to 'perception': Preference effects are indicated by the fact that the direction of performance change is determined by the way the primes are processed. The findings have recently been fit by a quantitative model called ROUSE that assumes: 1) Features of the primes are sometimes confused with those from the target flash. 2) The decision system matches the detected features to the choice word features. 3) The evidence from matching and mismatching features is discounted almost optimally when a choice word feature had also been in a prime word. This model fits many studies remarkably well, and suggests the priming task is a good model system for further investigations of the relation of memory to perception. The present project explores many aspects of this relation, including decision strategies and their determining factors, the nature of source confusion for features, the ways in which priming improves perception, the relation of accuracy to response time, and the relation to other attention and perception tasks. The data will serve as a base for further development of the ROUSE model for priming, and eventually a more complete model of perception,